restaurant problem

var restaraunt = {
    orders : [],
    order : function(order) {
        this.orders.push(order);
    },
    total : function(orders) {
        orders = orders || this.orders;
        return orders.reduce(function(total, order) {
            return total + order.cost;
        }, 0);
    },
    addVat : function() {
        return this.orders.map(function(order) {
            order.cost += Math.round(order.cost / 100 * 20);
            return order;
        });
    },
    getStarters : function() {
        return this.orders.filter(function(order) {
            return order.starter;
        });
    },
    getMains : function() {
        return this.orders.filter(function(order) {
            return order.main;
        });
    },
    isJustMains : function() {
        return this.orders.every(function(order) {
            return order.main;
        });
    },
    hasStarters : function() {
        return this.orders.some(function(order) {
            return order.starter;
        });
    },
    getFood : function(food) {
        return this.orders.find(function(order) {
            return order.starter === food || order.main === food;
        });
    }
};

restaraunt.order({ main : "Steak and chips", cost : 23.30 });
restaraunt.order({ starter : "Prawn Cocktail", cost : 5.99 });
restaraunt.order({ main : "Roast Dinner", cost : 19.99 });
restaraunt.order({ starter : "Soup of the day", cost : 4.99 });